Trace fossils as environmental indicators in the Corallian of England and Normandy

The distribution of trace fossils in Corallian (Upper Jurassic) rocks has been studied in three coastal areas in Yorkshire, Dorset, and Normandy. Three trace fossil associations, primarily related to the hydrodynamic conditions and only indirectly to depth, can be distinguished: the high-energy Diplocraterion association, and the low-energy Rhizocorallium and Teichichnus associations. The characteristic members of these associations can be used as environmental indicators throughout the Jurassic.     

Trace fossils as indicators of environmental change in Holocene sediments of the Archipelago Sea, northern Baltic Sea

Biogenic structures in Holocene sediments from the Archipelago Sea, northern Baltic Sea, were characterized through the analysis of X-ray images of four cores collected from water depths between 32 and 66 m. In the area, initial colonization of endobenthic invertebrates occurred at 7800 ± 80 calendar years BP. The trace assemblage at this level is low-diversity, small-diameter, shallowly tiered, and Palaeophycus-dominated; rare Arenicolites are also observed. Early colonization coincides with increasing marine influence in the post-glacial lacustrine setting just before the dramatic onset of brackish-water conditions established after 7600 BP. The post-incursion brackish-water assemblage possesses a higher diversity of traces (Planolites, Arenicolites, Lockeia, Teichichnus), which is taken to reflect the enhanced salinity and trophic state of the basin. The shift from Palaeophycus-mottling to a Planolites-dominated fabric represents changed behavioural patterns in the endobenthic community due to changed substrate properties. The ethology of the succeeding trace assemblage also represents a switch from domicile-based activities, such as predation, scavenging and interface-dominated deposit feeding to shallow-tier deposit feeding. Finally, traces are excluded from thinly laminated intervals, demonstrating that seafloor oxygen deficiency commonly reached levels that were detrimental to colonization of the sediment substrate.     

The trace fossils of the Baggy Beds (Upper Devonian) of North Devon,England

The trace fossils of the Baggy Beds are described. They includeTeichichnus cf.rectus Seilacher,Monocraterion cf.tentaculatum Torell,Diplocraterion yoyo sp. nov.,Arenicolites curvatus sp. nov., and other forms insufficiently well preserved for generic assignment. The protrusive and retrusive behaviour pattern ofD. yoyo is interpretated as a response to repeated phases of sedimentation and erosion and as a measure of these.A. curvatus is preserved in two modes: in the position of formation and as eroded tubes in conglomerates. The second reveals that the sediment around the tube was cemented to a thickness equal to the diameter of the tube.     

Organic-walled dinoflagellate cysts as paleoenvironmental indicators in the Paleogene; a synopsis of concepts

The organic-walled, hypnozygotic cysts of dinoflagellates (“dinocysts”) provide a rich, albeit incomplete, history of this eukaryotic plankton group in ancient sediments. Building on pioneering studies of the late 1970s and 1980s, recent ocean drilling and more detailed, integrated studies of surface sections have provided a wealth of dino-cyst data spanning the entire Paleogene. Based on multidisciplinary approaches, these studies have been instrumental in refining existing and furnishing new concepts of Paleogene paleoenvironmental and paleoclimatic reconstructions by means of dinocysts. Since dinocysts typically exhibit high abundances in neritic settings, the dinoeyst-based environmental and paleoclimatic information is complementary to that derived from typically more offshore groups such as planktonic foraminifera, coccolithophorids, diatoms, and radiolaria. While in a recent paper we gave a broad overview of case studies from around the globe (Sluijs et al. 2005), here we focus on a summary of these analyses and present a synopsis of applied paleoecological concepts in Paleogene (65–24 ma) dinocyst studies. Representing Earth’s greenhouse-icehouse transition, this episode holds the key to the understanding of extreme transient climatic change. The present paper offers guidelines for the application of dinocyst palaeoecology to the reconstruction of Paleogene sea-surface productivity, temperature, salinity, stratification, and paleo-oxygenation as well as their application in sequence stratigraphy, oceanic circulation and general watermass reconstructions.      

Devonian Trace Fossils of the Horlick Formation,Ohio Range,Antarctica: Systematic Description and Palaeoenvironmental Interpretation

The clastic Horlick Formation contains an ichnofauna of 28 ichnotaxa dominated by burrowers. These are a mixture of simple vertical forms (Skolithos linearis, S. magnus, Bergaueria cf. langi, Rosselia socialis, Monocraterion isp.), U or arc-like forms (Diplocraterion parallelum, Arenicolites types A and B, Catenarichnus antarcticus, C. isp., aff. Lanicoidichna isp.), and complex, vertical spiral structures (Asterosoma isp., Spirophyton isp.). Horizontal burrows include Ancorichnus cf. capronus, Palaeophycus tubularis, and Psammichnites devonicus isp. nov. Surface traces comprise Haplotichnus isp., Cruziana problematica, C. rhenana, Rusophycus aff. carbonarius, R. isp., Protovirgularia rugosa, Lockeia ornata and cubichnia indet., while trackways include Diplichnites gouldi, D. isp., Maculichna? isp. and large imprints. The Horlick Formation (maximum 56 m) records an early Devonian transgression onto a deeply weathered land area that lay in the direction of Marie Byrd Land, spreading from the South Africa sector of Gondwana. Analysis of the trace fossils confirms their formation in near-shore to intertidal environments, with some ichnotaxa living close to the marine/fluvial boundary (e.g., Spirophyton, aff. Lanicoidichna, Cruziana problematica, Rusophycus aff. carbonarius, Maculichna?). The ichnofauna probably comprised a variety of marine suspension and deposit-feeding worms, shallow burrowing molluscs (bivalves and possibly bellerophontids) and several different types of arthropods, including trilobites.     

Trace fossils from Lower Miocene (Ottnangian) molasse deposits of Upper Austria

Lower Miocene siliciclastic sediments of the Vöckla Schichten and Atzbacher Sande, Austria, contain a shallow-water trace-fossil assemblage of the Cruziana ichnofacies includingSkolithos isp.,Planolites ? beverleyensis, Ophiomorpha annulata, O.nodosa, Rosselia socialis, Cylindrichnus concentricus, Scolicia isp., andBichordites monastiriensis. The ichnogenusRosselia and the ichnospeciesRosselia socialis are revised. Analysis ofScolicia isp. andB. monastiriensis provides new information about their morphology and ichnotaxonomy.     

Vertebrate fossils of the Middle Devonian (Eifelian) Mühlenberg Formation in the Bergisches Land, northwestern Germany

Vertebrate fossils of the lower Middle Devonian Mühlenberg Formation from the western Bergisches Land (eastern Rhenish Massif) are described. The placoderms are represented by disarticulated plates of coccosteid arthrodires and the acanthodians by several ischnacanthid jaw bones and aMachaeracanthus finspine. The arthrodires are assigned to a new species; a new genus has to be erected if remains of trunk and head shield remains are conspecific.     

Trace fossils analysis of fluvial to open marine transitional sediments: Example from the Upper Devonian (Geirud Formation), Central Alborz,Iran

This study integrates ichnological and sedimentological data to interpret depositional environments of the mixed siliciclastic-carbonate fluvial to marine sediments of the Geirud Formation (Upper Devonian) in the central Alborz, northern Iran. Lithofacies analysis shows that these sediments are deposited in fluvial, tidal, shoreface, and shelf environments. Fluvial and tidal deposits are characterized by the presence of bi- to multi-directional cross beddings, reverse directional current ripples, low angle cross beddings, and herringbone cross beddings, with a few scattered Skolithos and Palaeophycus. Shoreface sediments, accumulated in a storm-influenced setting, are characterized by a preferentially interface and low diversity Cruziana ichnoassemblage (Rhizocorallium, Thalassinoides, Palaeophycus, Chondrites, and Ophiomorpha). In contrast to the fluvial-tidal assemblage, the storm-influenced shelf sediments display a highly diversified, mixture of dwelling and feeding forms (Arenicolites, Protovirgularia, Diplocraterion, Palaeophycus, Thalassinoides, Chondrites, and Helminthopsis), reflecting the presence of adequate food resources both in substrate and water column under normal salinity conditions. A fluvial-shelf replacement of the weakly to scarcely bioturbated sediments by the Rhizocorallium-Thalassinoides suite (Cruziana) – Chondrites-Helminthopsis (distal Cruziana) suite from the lower to upper parts of the succession clearly indicates an overall deepening upward in the Geirud Formation. In contrast to the lower part, generally of restricted environment, the upper part of the succession mainly shows open marine conditions. Ichnofabric development is controlled primarily by depositional conditions, e.g., bottom water oxygenation, sediment type, food abundance, and hydrodynamic level, which all exert control on substrate colonization style.     

Trace fossils from the Cambro-Ordovician cow head group,newfoundland, and their paleobathymetric implication

U-shaped burrows identified as the trace fossil Arenicolites occur in the Cambro-Ordovician Cow Head Group, a series of thin-bedded limestones interbedded with graptolitic shale and thick beds of limestone breccia and conglomerate. The lithology, limestone petrography, and trace fossils indicate deposition on a submarine slope of a slowly submerging carbonate platform. The limestone bed containing Arenicolites probably represents a period of slow deposition. The steeply inclined U-shaped burrows are assumed to have been formed by polychaete worms of the family Mochtyellidae which thrived in an argillaceous carbonate mud bottom of a carbonate platform slope, in depths exceeding 200 m. Although Arenicolites is believed to denote a shallow-water environment, its presence in the Cow Head extends the ecological niche of the Arenicolites-producing organisms into the outer shelf and continental slope. The domichnia of suspension feeders thus extends from shallow- to deep-water environments.     

Trace element associations as indicators of sediment accumulation in lakes

A geochemical study of lacustrine sediments was undertaken as part of a major paleolimnological project concerned with the impact of man on lakes. Factor analysis was applied to the geochemical data obtained from a core from one lake. Three principal factors which explained most of the variance of the initial data were identified. Factor I is related to the organic:mineral component ratio of the sediment, and can be considered as an indirect index of change in lake trophic status through time. Factor II is related to the granulometric composition of the sediment and matches evidence for changes in the hydrological regime of the lake. Factor III reflects changes in redox potential and is more closely related to processes occurring within the lake than other factors. Specific geochemical associations of elements are connected with each factor and are the factor indicators. The correlation of these associations are analyzed as geochemical indices of the variability of sediment accumulation conditions in time.     

Hydrography and biochemical indicators of microplankton biomass in the Bransfield Strait (Antarctica) during January 1994

 The relationships between hydrography and spatial distribution of several biochemical indicators of microplankton biomass (chlorophyll, protein and ATP) were studied in an area covering the eastern part of the Bransfield Strait and the northern part of the Weddell Sea, during Antarctic summer (January 1994). Four hydrographic zones were identified: (a) the northern part of the Bransfield Strait, covered by waters of Bellings- hausen Sea origin; (b) a Weddell Sea water mass that affected most of the study area; (c) the Weddell-Scotia Confluence waters, observed north of Elephant Island; and (d) waters influenced by ice melting, found towards the southeastern part of the sampled area. The highest values of biomass indicators (chlorophyll a, ATP and protein) were found in the zones affected by ice-melting processes and in waters from the Bellingshausen Sea. The lowest values of all biochemical parameters were found in the Weddell Sea and in the Weddell-Scotia Confluence waters. A high variability in the hydrographic structure and the distribution of biochemical indicators was observed. The degree of stabilization of the water column, the depth of the upper mixed layer and the grazing pressure of herbivorous zooplankton played a major role in the development, accumulation and spatial variability of microplankton biomass. Received: 15 August 1995/Accepted: 18 February 1996     

Facies features and paleoenvironmental reconstruction of the Early to Middle Devonian syn-rift volcano-sedimentary succession (Padeha Formation) in the Eastern-Alborz Mountains,NE Iran

The Padeha Formation in the Eastern-Alborz Mountains (northeast Iran) is an Early to Middle Devonian syn-rift succession. Siliciclastic rocks (conglomerates, sandstones, mudstones, and red paleosols) to non-marine carbonates (yellowish calcretes, dolocretes, stromatolites, and sandy bivalve packstone) associated with volcaniclastic rocks (basalts or andesites and tuffs) are present in this succession. Facies analysis led to the recognition of three facies associations that are deposited in three terrestrial environments (alluvial fan, distal fan, and palustrine/lacustrine). Its sedimentary fill pattern and association with mafic volcaniclastic rocks indicate that this formation is related to the initial phase of a rift basin (intracratonic rift). Paleosols of this formation are good indicators for recognition of paleoenvironmental factors (climatic changes from semi-arid to sub-humid with annual fluctuation, small and short gross-like vegetation cover, subaerial exposure, very shallow lake, volcanic source rocks, and early meteoric diagenesis).     

Devonian tetrapod trackways and trackmakers; a review of the fossils and footprints

The earliest tetrapods are known from the Upper Devonian. Their remains are becoming better known from increasing numbers of specimens, localities, environments and ichnofossils. Each of the eight (or possibly nine) genera now represented by skeletal fossils is reviewed in its sedimentological, faunal and stratigraphic context, with an assessment of what might be inferred about the habitus and locomotory capabilities of each. Fossil trackways and their interpretations are then re-examined in the context of the known body forms, and consideration given to the degree of fit between the skeletal fossils, the trackways and their interpretations. The currently known Devonian tetrapods are unlikely to have made any of the known tracks, unless they were produced under water. Neither the skeletal fossils nor the trackways show good evidence of terrestrial locomotion among Devonian tetrapods. When the fossil material and recent phylogenetic analyses are taken in combination, it appears that neither tetrapods nor limbs with digits are likely to have arisen before the Frasnian. This should be borne in mind in palaeoecological studies of these animals.     

Patagonian ostracods as indicators of climate-related hydrological variables: implications for paleoenvironmental reconstructions in Southern South America

Different precipitation regimes across Patagonia generate an environmental gradient that is expected to reflect upon the solute composition and concentration of lake water through the ensuing differences in water balance. In turn, this hydrochemical gradient could influence the occurrence and distribution of ostracods in the area. A cluster analysis on hydrochemical data of 36 Southern Patagonian waterbodies shows that low salinity, bicarbonate-dominated waters characterize Andean and ecotonal lakes, located in the wetter part of the precipitation gradient, while their steppe counterparts, which receive a much lower precipitation input, are more saline, enriched in all major anions and sodium-dominated. Kruskal–Wallis tests followed by Mann–Whitney pairwise comparisons show statistically significant differences in the ostracod species each water type hosts, with L. patagonica, E. cecryphalium, P. smaragdina and P. incae being found in the more dilute waters characteristic of Andean and ecotonal lakes and Limnocythere rionegroensis in the mesohaline, evaporatively evolved waters typical of steppe lakes. Other species studied do not appear to have such distinct distributions, having been found throughout the range of conditions studied. These findings promote the use of the aforementioned ostracods as semi-quantitative paleohydrological indicators, which could improve paleoclimatic reconstructions in Patagonia.     

Epizoic bryozoans and corals as indicators of life and post-mortem orientations of the Devonian brachiopod Meristella

The in-life and post-mortem orientations of the Lower Devonian brachiopod Meristella atoka from the Haragan Formation (Lower Devonian; south-central Oklahoma) are inferred from the distribution of epizoic bryozoans and the orientations of base plates of epizoic corals. Three bryozoans, Cyphotrypa corrugata, Fistuliporella maynardi and Leioclema pulchellum, and one coral, Favosites conicus, are considered. Most zoaria that contact the commissure terminate at the commissurc, and a few zoaria terminate at growth lines. This suggests that the bryozoans were primarily life associates of Meristella atoka. Collectively, these three bryozoan species most extensively encrusted marginal sectors of the brachial valve and are very rare on the posteromedian sector (the umbo) of the pedicle valve. This distributional pattern indicates that the preferred living orientation of Meristella atoka was umbo-down (posteromedian sector of the pedicle valve resting on or buried in the substratum) with the commissure steeply inclined to the sediment water interface. Most coralla of Favosites conicus that contacted the commissure encrusted over the commissure. This indicates that Favosites conicus either preferentially encrusted Meristella atoka post-mortem or colonized living brachiopods but subsequently caused them to die. Furthermore, Favosites conicus most extensively encrusted anterior sectors of the brachial valve, especially the fold. The lateral and anterior orientations of the commissure with respect to the base plates (holothecae) of Favosites conicus indicates that the brachiopods were oriented approximately horizontal with respect to the base plates. This suggests that the preferred post-mortem orientation of Meristella atoka was resting nearly horizontally on the substratum. These data and interpretations confirm previously inferred in-life orientations of Meristella atoka and are consistent with post-mortem orientations hypothesized for elongate-oval athyrid brachiopods. □Brachiopoda, Athyridacea, Meristella atoka , palaeoecology, autecology, epizoans, bryozoans, corals, sedimentology, Lower Devonian, North America, Oklahoma.     

First discovery of Pleistocene orangutan (Pongo sp.) fossils in Peninsular Malaysia: Biogeographic and paleoenvironmental implications

Nine isolated fossil Pongo teeth from two cave sites in Peninsular Malaysia are reported. These are the first fossil Pongo specimens recorded in Peninsular Malaysia and represent significant southward extensions of the ancient Southeast Asian continental range of fossil Pongo during two key periods of the Quaternary. These new records from Peninsular Malaysia show that ancestral Pongo successfully passed the major biogeographical divide between mainland continental Southeast Asia and the Sunda subregion before 500 ka (thousand years ago).     

毛翅目化石研究进展

本文详细总结和回顾了世界毛翅目化石研究简史,列出已发表的化石种类名录、分布及年代,共37科、193属、661种(包括中国发现的4科9属15种),描述了不同地质时期主要毛翅目化石的分类单元和分布地区。简要介绍了毛翅目分类系统及系统发育、不同地质时期毛翅目化石的产地及时代。初步分析了目前该类群所存在的一些问题,并对今后的研究工作进行了展望。     

Three new species of Diphascon of the pingue group (Eutardigrada,Hypsibiidae) from Antarctica

This paper contributes to the knowledge of the pingue group of species within the genus Diphascon. Three new species are described, Diphascon (D.) polare, D. (D.) dastychi and D. (D.) victoriae, from Victoria Land (Antarctica); they differ from other species of the pingue group in characters of the bucco-pharyngeal apparatus. D. polare and D. victoriae differ also in the claw shape. A key is provided to the Diphascon pingue group. Accepted: 30 November 1998